"Even if Iran wanted to go for a nuclear weapon, it would not be before the end of this decade or sometime in the middle of the next decade," he said, adding that this estimate echoed the view of US intelligence agency, the CIA.

The US and its European allies have rejected Mr ElBaradei's suggestion that Iran be allowed to keep part of its enrichment programme.

In March, the UN Security Council imposed a second round of sanctions on Iran for failing to suspend uranium enrichment, prompting Tehran to limit its co-operation with the IAEA.

The BBC's diplomatic correspondent, Jonathan Marcus, says Washington may have some difficulty in persuading all members of the UN Security Council to impose further sanctions.